1. Field of the Invention
This invention relates to a chuck assembly, more particularly to a chuck assembly with a cooling mechanism for cooling a hydraulic fluid in a clearance between a shaft and a sleeve of the chuck assembly.
2. Description of the Related Art
U.S. Pat. No. 6,497,417 discloses a conventional chuck assembly 1 that includes a housing 10 defining an inner space, a shaft 11 mounted co-axially and rotatably in the inner space and defining a chuck-receiving space 13 which has an enlarged end portion defining a piston-receiving chamber 131, a sleeve 12 secured to the housing 10 and sleeved on the shaft 11 so as to define a clearance 14 therebetween, a bearing unit 18 disposed between the sleeve 12 and the shaft 11, a chuck unit mounted in the chuck-receiving space 13 and including a plurality of jaws 16 for holding a workpiece (not shown), and a piston 15 mounted in the piston-receiving chamber 131, displaceable in an axial direction, and connected to the jaws 16 in such a manner that axial displacement of the piston 15 results in radial displacement of the jaws 16. The piston 15 subdivides the piston-receiving chamber 131 into first and second compartments 1311, 1312. A fluid channel 17 is formed in the chuck assembly 1, is in fluid communication with the first compartment 1311 of the piston-receiving chamber 131, and is adapted to be connected to a hydraulic fluid supply (not shown) so as to permit flow of pressurized hydraulic fluid into the first compartment 1311, thereby resulting in axial displacement of the piston 15.
Since the shaft 11 is operated at a relatively high speed, a relatively large amount of heat is generated due to friction between the shaft 11 and the sleeve 12, which significantly increases the temperature of the hydraulic fluid in the clearance 14, which, in turn, results in an adverse effect on the performance of the chuck assembly 1.
The disclosure of U.S. Pat. No. 6,497,417 is incorporated herein by reference.